Reversible electrochemical mirrors can be used to alternatively reflect or transmit light and thus are useful in building windows, automotive mirrors, on orbital platforms, and the like. See U.S. Pat. No. 6,400,491.
An electrochemical mirror typically includes a transparent substrate, a transparent conductive working electrode on the transparent substrate, a counter electrode, and an electrolyte material between the working electrode and the counter electrode.
The application of a negative potential across the two electrodes causes electroplating of the metal ions (silver, copper, gold, and the like) on the surface of the working electrode forming a mirror film. Application of a less negative potential or a positive voltage across the working electrode and the counter electrode oxidizes and dissolves the metal mirror film permitting the transmission of radiation through the electrodes, the electrolyte, and the substrate.